Reproduction of Diaeretiella rapae on Russian wheat aphid hosts at different temperatures

Diaeretiella rapae (M'Intosh), a polyphagous and cosmopolitan parasite of aphids, was imported from China to the USA for biological control of Diuraphis noxia (Mordwilko), a pest of small grains. We studied several aspects of its biology on D. noxia hosts in the laboratory at 3 constant temperatures, 10.0, 21.1, and 26.7 °C. Females lived significantly longer than males at all 3 temperatures, and longevity was greatest at 10 °C, followed by 21.1 and 26.7 °C. Fecundity (= number of mummies) did not differ significantly among the 3 temperatures studied. The ovarian egg-load was 129.1 ± 9.3, and was significantly affected by the size of adult females. A pre-oviposition period ± 0.26 days) was detected at 10 °C, but not at the other temperatures. Pre-imaginal survivorship was similar among temperatures, while R _o and T _c decreased with temperature, and r _m increased with temperature. The offspring sex ratio (proportion females) was lowest at 26.7 °C, and similar between 10.0 and 21.1 °C. In addition, the offspring sex ratio significantly declined with the age of the female parent. The suitability of D. rapae for colonization against D. noxia in North America is discussed in relation to its responses to temperature and the climate of its home range.     

Thermal acclimation in the grain miteAcarus siro (Acari: Acaridae)

Grain mites reared on wheat germ at 21±1°C and 85% r.h. were treated (acclimated) as adults at 0, 14, 28 or 33°C for 1 or 4 days. Fecundity, longevity and numbers of F₁ females and males produced were compared. A treatment of 1 day was enough to acclimateAcarus siro and change the studied developmental parameters. Acclimation always lowered fecundity but the magnitude of the effect was dependent upon the temperature regime. The number of males and females emerging differed greatly among various temperature regimes; however, the sex ratio of emerged adults remained in most instances quite constant.     

Adaptive significance of egg size plasticity in response to temperature in the migrant skipper, Parnara guttata guttata (Lepidoptera: Hesperiidae)

Females of the migrant skipper, Parnara guttata guttata, that are reared under lower temperatures lay smaller eggs. The adaptive significance of egg size plasticity in response to temperature is unknown in this species. We suggest, based on the following experimental results, that P. g. guttata uses temperature as an indirect cue to predict the host condition (leaf toughness) of the next generation. First, larvae were reared under the typical conditions of temperature and photoperiod experienced during the immature stages in the first, second, and overwintering (third) generations (LD 16:8 at 25°C, LD 14:10 at 25°C and LD 14:10 at 20°C). Females reared under LD14:10 at 20°C produced more, smaller eggs than those reared under LD14:10 and LD16:8 at 25°C. Secondly, survival rates of first instar larvae derived from females reared under the three photoperiod/temperature treatments were measured on young soft rice leaves (soft), or tough, old rice leaves (tough). Survival rates of hatchlings reared on soft and tough leaves did not differ when females were reared under LD16:8 and LD14:10 at 25°C. However, hatchling survival was significantly higher on soft than on tough leaves when females were reared under LD14:10 at 20°C. Thirdly, we found that egg size plasticity in response to temperature in P. g. guttata may be a threshold response. Temperatures below 20°C experienced during the immature stages may be effective for production of smaller and more eggs in the overwintering generation of P. g. guttata.     

Life-cycle of Suidasia medanensis (=pontifica) (Acari: Suidasiidae) under laboratory conditions in a tropical environment

The life cycle of Suidasia medanensis (= pontifica) was studied under laboratory conditions at 26°C and 86% relative humidity. Freshly laid eggs were observed until they developed into adults and the periods between stages were recorded. Production of eggs by mated females was monitored until they died. The eggs required an average of 12.6 ± 0.6 days to develop into adults. Mean longevity of mated females and males was similar (48.6 ± 13 and 49.1 ± 20 days, respectively). The conditions used in this study may be considered optimal for in vitro culture of S. medanensis.     

Photoperiod and temperature studies to determine whether diapause is found in successive generations of the African phytoseiid,Euseius fustis (Pritchard and Baker) (Acari: Phytoseiidae)

Photoperiod and temperature conditions known to induce diapause in tropical arthropods were tested on two generations (G₀ and G₁) of the phytoseiid, Euseius fustis. Failure to lay eggs or a pre-oviposition period longer than 15 days were the criteria used to determine whether females were in diapause. Females reared from egg to adult and held throughout adult life under cyclic temperatures of 29/20°C in combination with long photophases of 16L: 8D and 14L: 10D showed no indication of aestival diapause. Similarly, hibernal diapause was not induced in females reared under a constant temperature of 18°C and a photophase of 8L: 16D. Under the various test conditions, females initiated oviposition within an average of 4 days. Overall, pre-oviposition patterns for G₀ and G₁ females were similar under the same test conditions. Reproductive patterns based on the mean number of eggs per female per day varied only slightly between generations for the same treatments. No behavioural or morphological attributes associated with diapause were observed.     

Life Tables of Phytoseiulus Macropilis (Banks) (Gamasida: Phytoseiidae) at Different Temperatures

The biology of Phytoseiulus macropilis (Banks) fed on Tetranychus urticae Koch was studied at different temperatures. The total development times averaged 7.5, 5.7, 4.2, 4.2 and 5.6 days at 20, 25, 28, 30 and 32°C, respectively at 78 ± 2% RH and 16 h photoperiod daily. The intrinsic rate of natural increase (r _m) and the net reproduction (R _o) reached maximum values 0.47 and 88.9, respectively, at 28°C. The mean generation time decreased (20.0-8.8 days) with increasing temperature 20-28°C.     

Life history of Euseius scutalis feeding on citrus red mite Panonychus citri at various temperatures

The aim of this study was todetermine the biology and reproductivepotential of Euseius scutalis(Athias-Henriot) (Acari: Phytoseiidae) atvarious temperatures. These data are of valuein relation to mass rearing and the developmentof population dynamics models. The developmenttime, survival and fecundity of E.scutalis were determined at 20, 25 and30 ± 1 °C, 65 ± 10% RH and 16:8photoperiod. Total development times of E.scutalis were 6.7, 4.9 and 4.2 days at 20, 25and 30 ± 1 °C, respectively, using adiet of all life stages of the spider mite Panonychus citri (McGregor) (Acari:Tetranychidae). In general, preoviposition andpostoviposition periods of E. scutaliswere shortened as temperature increased, butthe oviposition period was longer at 25 °C than at 20 and 30 °C. Theshortest survival time of E. scutalis, at30 °C, was 10.1 days, followed by 23.7days and 28.6 days at 20 and 25 °C,respectively. Mated females laid on average1.1, 1.4 and 1.7 eggs per female per day and21.5, 39.7 and 17.1 eggs over their entire lifetime at 20, 25 and 30 °C, respectively.The sex ratios of E. scutalis were2.11/1, 2.24/1 and 2.11/1 female/male at 20, 25and 30 °C, respectively. The intrinsicrate of natural increase (r _m) increasedwith rising temperatures from 0.166 at 20 °C to 0.295 females/female/day at 30 °C. The net reproductive rate (R ₀)was highest at 25 °C (26.03females/female) and lowest at 30 °C(12.95 females/female). Mean generation time(T ₀) was longest at 25 °C (17.50days) and shortest (9.53 days) at 30 °C.     

Development, survival and reproduction of Euseius finlandicus (Acari: Phytoseiidae) at different constant temperatures

Development, survival and reproduction of Euseius finlandicus Oudemans were studied at seven constant temperatures (15, 20, 25, 27, 30, 32 and 34°C) in the laboratory. Within the temperature range tested, developmental period from egg to adult varied from 148 to 360.5h and 133.7 to 336.5h for females and males, respectively. The lower thermal threshold for immature development for females and males was 8.9 and 6.4°C, respectively. Survival during immature development exceeded 90% at all the temperatures from 15 to 32°C, but at 34°C an abrupt decline was recorded. Female longevity decreased gradually from 82.7d at 15°C to 12.2 d at 34°C. The mean generation time ranged from 44.3d at 15°C to 15.9d at 32°C. The highest r _m value (0.2817) was obtained at 30°C and the lowest at 15°C (0.0976). Temperatures above 30°C had an adverse effect on population increase.     

Seasonal dynamics of metabolic activity of the Daphnia community in Lake Bled (Slovenia)

Seasonal changes of the community composition, oxygen consumption (R) and respiratory electron transport system (ETS)-activity of the Daphnia community living in Lake Bled (Slovenia) were studied between January and December 1998. The ETS activity of ovigerous Daphnia females at in situ temperature ranged from 3.27 l O₂ mg dw^–1 h^–1 in February to 20.91 l O₂ mg dw^–1 h^–1 in July. Respiration rates at in situ temperature varied from 4.04 l O₂ mg dw^–1h^–1 in December to 18.68 l O₂ mg dw^–1 h^–1in July. The influence of four factors (temperature, body size, fecundity, genetic differences) on the metabolism were investigated. Both ETS activity and respiration rate significantly correlated with temperature. The proportion of hybrid D. cucullata× galeata in Daphnia community correlated significantly with respiration rate at in situtemperature and ETS activity at standard temperature also. ETS activity and respiration rate showed no significant correlation with body size and the fecundity of Daphnia, whereas ETS activity in D. hyalina × galeata and D. cucullata× galeataseparately correlated with body size. ETS activity of D. hyalina × galeata also was correlated with fecundity. Hybrid D. hyalina× galeata had up to one third lower ETS activity than D. cucullata× galeata. The mean ETS/R ratio in the Daphnia community was 1.16±0.28 (N= 12). The ETS/R ratio did not correlate significantly with temperature, body size, fecundity or the proportion of D. cucullata× galeatain the Daphnia community. Laboratory experiments showed that both hybrids had similar ETS/R ratios.     

Seasonal and daily rhythms of body temperature in the European hamster (Cricetus cricetus) under semi-natural conditions

Body temperature of five European hamsters exposed to semi-natural environmental conditions at 47° N in Southern Germany was recorded over a 1.5-year period using intraperitoneal temperature-sensitive radio transmitters. The animals showed pronounced seasonal changes in body weight and reproductive status. Euthermic body temperature changed significantly throughout the year reaching its maximum of 37.9±0.2°C in April and its minimum of 36.1±0.4°C in December. Between November and March the hamsters showed regular bouts of hibernation and a few bouts of shallow torpor. During hibernation body temperature correlated with ambient temperature. Monthly means of body temperature during hibernation were highest in November (7.9±0.8°C) and March (8.2±0.5°C) and lowest in January (4.4±0.7°C). Using periodogram analysis methods, a clear diurnal rhythm of euthermic body temperature could be detected between March and August, whereas no such rhythm could be found during fall and winter. During hibernation bouts, no circadian rhythmicity was evident for body temperature apart from body temperature following ambient temperature with a time lag of 3–5 h. On average, hibernation bouts lasted 104.2±23.8 h with body temperature falling to 6.0±1.7°C. When entering hibernation the animals cooled at a rate of -0.8±0.2°C·h^-1; when arousing from hibernation they warmed at a rate of 9.9±2.4°C·h^-1. Warming rates were significantly lower in November and December than in January and February, and correlated with ambient temperature (r=-0.46, P<0.01) and hibernating body temperature (r=-0.47, P<0.01). Entry into hibrnation occured mostly in the middle of the night (mean time of day 0148 hours ±3.4 h), while spontaneous arousals were widely scattered across day and night. For all animals regression analysis revealed free-running circadian rhythms for the timing of arousal. These results suggest that entry into hibernation is either induced by environmental effects or by a circadian clock with a period of 24 h, whereas arousal from hibernation is controlled by an endogenous rhythm with a period different from 24 h.Abbreviations bw body weight - CET central European time - T _a ambient temperature - T _b body temperature - TTL transistor-transistor logic     

Effect of temperature on reproductive parameters and longevity of <Emphasis Type="Italic">Tyrophagus putrescentiae</Emphasis> (Acari: Acaridae)

The effect of temperature on reproductive parameters and longevity of the mold mite, Tyrophagus putrescentiae (Schrank) was examined at seven constant temperatures, ranging from 10 to 34 °C, and a relative humidity of 90±5%. Preoviposition period and fecundity were adversely affected by extreme temperatures and the oviposition period increased as temperature was reduced. Different patterns were observed for longevity data for males and females, with greater longevities for males at intermediate temperatures and more similar values for both sexes at extreme temperatures. Polynomial and non-linear models provided a good fit of the relationship of reproductive and longevity parameters with temperature. The effect of temperature on the intrinsic rate of increase of T. putrescentiae populations was established by the non-linear Lactin model. The optimum temperature for development was obtained at 30 °C. At this temperature, the population doubling time is 1.75 days. The lower and upper thresholds for T. putrescentiae populations were established at 10.4 and 34.8 °C, respectively. Altogether, these data provide basic information to develop sound physical control strategies of the mold mite.     

The energetics of the common mole rat Cryptomyś, a subterranean eusocial rodent from Zambia

Body temperature, oxygen consumption, respiratory and cardiac activity and body mass loss were measured in six females and four males of the subterranean Zambian mole rat Cryptomys sp. (karyotype 2 n=68), at ambient temperatures between 10 and 35°C. Mean body temperature ranged between 36.1 and 33.2°C at ambient temperatures of 32.5–10°C and was lower in females (32.7°C) than in males (33.9°C) at ambient temperatures of 10°C but dit not differ at thermoneutrality (32.5°C). Except for body temperature, mean values of all other parameters were lowest at thermoneutrality. Mean basal oxygen consumption of 0.76 ml O₂·g^-1· h^-1 was significantly lower than expected according to allometric equations and was different in the two sexes (females: 0.82 ml O₂·g^-1·h^-1, males: 0.68 ml O₂·g¹·h^-1) but was not correlated with body mass within the sexes. Basal respiratory rate of 74·min^-1 (females: 66·min¹, males: 87·min^-1) and basal heart rate of 200·min^-1 (females: 190·min^-1, males: 216·min^-1) were almost 30% lower than predicted, and the calculated thermal conductance of 0.144 ml O₂·g^-1·h¹·°C^-1 (females; 0.153 ml O₂·g^-1·h^-1·°C^-1, males: 0.131 ml O₂·g^-1·h^-1·°C^-1) was significantly higher than expected. The body mass loss in resting mole rats of 8.6–14.1%·day^-1 was high and in percentages higher in females than in males. Oxygen consumption and body mass loss as well as respiratory and cardiac activity increased at higher and lower than thermoneutral temperatures. The regulatory increase in O₂ demand below thermoneutrality was mainly saturated by increasing tidal volume but at ambient temperatures <15°C, the additional oxygen consumption was regulated by increasing frequency with slightly decreasing tidal volume. Likewise, the additional blood transport capacity was mainly effected by an increasing stroke volume while there was only a slight increase of heart frequency. In an additional field study, temperatures and humidity in different burrow systems have been determined and compared to environmental conditions above ground. Constant temperatures in the nest area 70 cm below ground between 26 and 28°C facilitate low resting metabolic rates, and high relative humidity minimizes evaporative water loss but both cause thermoregulatory problems such as overheating while digging. In 13–16 cm deep foraging tunnels, temperature fluctuations were higher following the above ground fluctuations with a time lag. Dominant breeding females had remarkably low body temperatures of 31.5–32.3°C at ambient temperatures of 20°C and appeared to be torpid. This reversible hypothermy and particular social structure involving division of labour are discussed as a strategy reducing energy expenditure in these eusocial subterranean animals with high foraging costs.Abbreviations BMR basal metabolic rate - br breath - C thermal conductance - HR neart rate - LD light/dark - M _b body mass - MR metabolic rate - OP oxygen pulse - PCO₂ partial pressure of carbon dioxide - PO₂ partial pressure of oxygen - RMR resting metabolic rate - RR respiratory rate - T _a ambient temperature - T _b body temperature - TNZ thermal neural zone - O₂ oxygen consumption     

The effect of temperature on the pattern of torpor in a marsupial hibernator

Physiological variables of torpor are strongly temperature dependent in placental hibernators. This study investigated how changes in air temperature affect the duration of torpor bouts, metabolic rate, body temperature and weight loss of the marsupial hibernator Burramys parvus (50 g) in comparison to a control group held at a constant air temperature of 2°C. The duration of torpor bouts was longest (14.0±1.0 days) and metabolic rate was lowest (0.033±0.001 ml O₂·g^-1·h^-1) at2°C. At higher air temperatures torpor bouts were significantly shorter and the metabolic rate was higher. When air temperature was reduced to 0°C, torpor bouts also shortened to 6.4±2.9 days, metabolic rate increased to about eight-fold the values at 2°C, and body temperature was maintained at the regulated minimum of 2.1±0.2°C. Because air temperature had such a strong effect on hibernation, and in particular energy expenditure, a change in climate would most likely increase winter mortality of this endangered species.Abbreviationst STP standard temperature and pressure - T _a air temperature - T _b body temperature - VO₂ rate of oxygen consumption     

Mating Behavior and Reproductive Potential in the Turnip Moth Agrotis segetum (Lepidoptera: Noctuidae)

We investigated the lifetime mating potential and the reproductive behavior of male and female turnip moths Agrotis segetum (Schiff.) under field and laboratory conditions. The sex ratio was 1 : 1 in a lab-reared population as well as in two wild populations. Males were capable of mating repetitively a relatively large number of times (mean of 6.7 ± 2.7 matings) when given access to new virgin females throughout their lifetimes. Females seldom mated more than once (mean ± 1.3 ± 0.6 matings), indicating a male-biased operational sex ratio. The mean potential lifetime mating was five times higher in males, while the coefficient of variance was lower in males. There was no differences in longevity between animals that were allowed to mate and animals not allowed to mate, indicating no direct costs or benefits of mating in physiological terms. In males, the number of matings was positively correlated with longevity, but this was not the case in females. Nor was there a correlation between the number of female matings and the number of fertilized eggs. There was a negative correlation between the number of eggs fertilized and the number of times males had previously mated, indicating that male ejaculates were limited. Male spermatophore size also decreased with number of achieved matings. Laboratory-reared females attracted males in the field throughout their lifetimes, with a peak at 3–7 days of age. Wild males, allowed to choose between pairs of caged females in the field, were attracted in equal numbers to females of different ages. Females did not show any mate-rejection behavior in the field. They mated with the first male that courted them. No incidence of mate replacement by males arriving later to already courted females were recorded.     

Seasonal variations in the immune system of the tench,Tinca tinca (Cyprinidae): proliferative response of lymphocytes induced by mitogens

The proliferation of tench lymphocytes induced by mitogens was studied during the four seasons of the year. Fish were maintained under natural conditions of photoperiod and temperature (mean ± SD: 12±2°C in winter, 22±3°C in spring, 30±3°C in summer and 21±3°C in autumn). Cultures were performed in vitro at 22°C in all seasons and the results were compared. Subsequently, in seasons with extreme water temperatures, cultures in vitro were performed at the same temperature as that of the water (12°C in winter and 30°C in summer) and the results were compared seasonally at the seasonal temperature, i.e. at 22°C in spring, 30°C in summer, 22°C in autumn and 12°C in winter. Phytohemagglutinin, concanavalin A, lipolisaccharide from E. coli and pokeweed mitogen were used as mitogens. Studies performed at 22°C as assay temperature in all seasons showed profound seasonal changes: while in spring, summer and autumn the mitogenic response of lymphocytes to phytohemagglutinin, concanavalin A, lipolisaccharide from E. coli and pokeweed mitogen was very low, during winter the results obtained were significantly higher. However, when the assays were performed at the corresponding seasonal temperature the differences were not as pronounced between the different seasons, and the mitogenic responses of lymphocytes were found to be the lowest during the winter and the highest during the summer with all mitogens used. This fact suggests that immunosuppression occurs in winter and an immunostimulation occurs in summer. However, the higher response found in winter when assaying at 22°C suggests that this property of lymphocytes needs an assay temperature higher than the in vivo temperature in order to observe accurate mitogenic responses.Abbreviations Con A concanavalin A - cpm counts per minute - LPS E. coli lipolisaccharide - MS222 tricainemethane sulphonate - PBS phosphate-buffered saline - PHA phytohemagglutinin - PWM pokeweed mitogen - SI stimulation index     

Location,reproduction and movement of Neoseiulus californicus (Acari: Phytoseiidae) during the autumn,winter and spring in orchards in the south of France

Field samples and experiments conducted in apple orchards in the south of France showed that Neoseiulus californicus (McGregor) searched for prey on the trees and in the ground cover as late as mid-November 1993, and at least as early in the spring as the end of February 1994. Overwintering females fed, expanded and produced viable eggs within 7.9±0.3 (SE) days given the natural light regime, adequate food and temperatures of 17.0±20.6°C. The first generation of N. californicus developed in the field during March and April 1994. N. californicus nymphs, females and males readily moved over bare ground and through a grass ground cover to trap plants located on stakes 1 m above the ground. In the laboratory, the rate of movement of adult females on 0.5 mm copper wire was a linear function of temperature above a threshold of 11.9±0.9°C. At 25°C they travelled 10 m per h. The migration rate of N. californicus to trap plants on stakes placed in an orchard 13 Apr. increased in 2 weeks from 0.07 to 0.57 predators/trap plant/degree-day, while the migration rate to plants placed directly in the ground cover was 1.45 predators/trap plant/degree-day. The largest population of N. californicus in April occurred on Barley, Hordeum murinum L. This plant produces pollen in April and May, and may be useful in biocontrol programs.     

Sex Differences in Olfactory Communication in Saguinus labiatus

We assessed behaviors involved with depositing and receiving scent in three captive heterosexual pairs of red-bellied tamarins (Saguinus labiatus). The frequencies of scent deposition and scent investigatory behaviors differed between the sexes. Females scent marked exclusively by the anogenital gland. Males deposited 95.8% of scent marks via the anogenital gland and 4.2% via the sternal gland. Females scent marked at a significantly higher rate than that of males (0.9 ± 0.1 versus 0.3 ± 0.1 per 20 min, respectively). Males investigated the scent of their opposite-sex partners whereas females investigated no male scent. Mean ± SEM latency for males to investigate female scent was 208.7 ± 65.0 sec. Around 9% of all scent marks were overmarked within 8 min and there was a nonsignificant trend for males to overmark the scent of their female partners than vice versa. We discuss the sex differences in olfactory communication in red-bellied tamarins in terms of sexual selection theory.     

Diel patterns of activity of Thymelicus lineola adults (Lepidoptera: Hesperiidae) in relation to weather *

ABSTRACT. 1. Daily patterns of activity, thoracic temperature (T_th) and thermoregulatory behaviour in relation to environmental conditions were studied in the European skipper Thymelicus lineola (Ochsenheimer) adults. 2. Daily activity was limited mainly by T_th, which in turn was dependent on air temperature (T_a) and sunlight. However, when light intensity fell to < 100 W m^?2, skippers also became inactive. 3. T_th was sometimes as much as 12°C above T_a, and this was most pronounced under cool conditions when basking activity predominated. 4. Black globe temperature (T_bg) which, in the absence of wind, is influenced by both T^a, and radiant heat load in a manner similar to a basking butterfly, was used to approximate the maximum T_th attained by T.lineola through basking. 5. Both males and females basked at T_bg >20°C, and if this temperature was not attained, skippers remained inactive. As T_bg increased, basking activity declined more rapidly in males than in females. Basking bouts were also shorter in males. 6. Males also flew, fed and courted females at T_bg >20°C, while females only fed and flew at T_bg >22°C. The percentage of both sexes feeding and flying, and courting in the case of males, were positively correlated with T_bg. 7. In warm weather, males divided their time equally between flying and feeding, while females spent the majority of their time feeding. Feeding bouts were shorter and flying bouts were longer in males than in females. Flight duration in males was positively correlated with T_bg. 8. Skippers avoided, and, consequently laid fewer eggs in, shady areas. 9. Sexual differences in activity patterns in relation to weather reflect differences in the reproductive requirements of the two sexes.     

The effect of temperature on development and fecundityof Scymnus levaillanti

Development and fecundity of Scymnus levaillanti(Mulsant) were recorded at fiveconstant temperatures ranging from 15 to 35 ± 1 °C in 5 °C increments, 60 ± 5% RHand 16 h of artificial light (5000 Lux). Developmentaltime (egg to adult) of S. levaillantisignificantly decreased with increasing temperatures,ranging from 63.9 days at 15 °C to 11.1 days at35 °C. Development from egg to adult required305.2 DD above a developmental threshold estimated as11.7 °C. Oviposition periods lasted 86.5, 76.1,47.2, and 31.5 days at 20, 25, 30 and 35 °C,respectively. No eggs were deposited at 15 °C.Higher temperatures resulted in shorter generationtimes (T_O) and in decreased net reproductiverates (R_O) of the coccinellid. S.levaillanti kept at 30 °C produced 0.151females/female/day, the highest per capita rate ofpopulation growth (r_m). The `functional response'of larvae and adults of S. levaillanti matcheswell that described by Holling (1959) as Type 2.Daily number of eggs deposited by females increased toa plateau with increasing prey density. Resultsobtained here provide information about the biology ofS. levaillanti, and its feeding capacityindicates that it may act as an important control agent.     

Respiratory metabolism of Cyclops bicuspidatus (sensu stricta) (Claus) (Copepoda: Cyclopoida) from Esthwaite Water,Cumbria

Summary The respiration rate of all stages of Cyclops bicuspidatus (s. str.) (Claus), a benthic copepod, from Esthwaite Water in the English Lake District, was determined at a range of field temperatures, 4° C–12° C, using cartesian diver microrespirometry. The population of C. bicuspidatus in Esthwaite Water was found to be adapted to low temperatures, with an optimum rate of metabolism at 8° C. Weight varied with temperature, in general the largest weights occurred at the lower temperatures. Adult males had higher rates of respiration than adult females, which were on average twice the size of males. Gravid and non-gravid females had similar levels of metabolism. Regression coefficients (b), derived from regressions of log oxygen consumption against log dry weight were low, ranging between 0.25–0.51 according to temperature.